In this thesis, a second-order low pass square root domain filter (SRD filter) based on operational transconductors amplifiers (OTAs) is presented. The SRD filter consists of two translinear filters and four OTAs. Because the OTA has small voltage swings, which may violate the large signal natural of the SRD filter. We investigate the dynamic range of this compact SRD filter with different quality factor(Q). The circuit has fewer numbers of transistors and operate in low voltage, therefore, it has less power consumption and less chip area. The circuit has been fabricated with 0.35£gm CMOS technology. It operates with a supply voltage 1.5V and the biasing current varies from 10uA to 80uA. Measurement results lts show that Im/I0≥40% when the external capacitance C is 3.5pF¡B7pF and Im/I0≥53% when the external capacitance C is 3pF¡B8.5pF. The cutoff frequency of the filter can be tuned from 1.24MHz to 5.53MHz when the external capacitance C is 3.5pF¡B7pF and the cutoff frequency can be tuned from 900KHz to 4.46MHz when the external capacitance C is 3pF¡B8.5pF. The total harmonic distortion is 0.908% and the power consumption is 506£gW.

Conventional gm-c filters have limited voltage swings in low voltage operation. CMOS companding filters replace gm-c filters in low voltage environment for high dynamic range. The square-root domain filter and log-domain filter belongs to this companding filter category. In this thesis, a second order low pass square root domain filter (SRD filter) based on the up-down TL (translinear loop) circuit structure is presented. The SRD filter consists of four geometric-mean cells and three squarer/divider cells. The advantages of the proposed circuits are low supply voltage, low power consumption, high bandwidth, and low total harmonic distortion (THD). The circuit has been fabricated with 0.35£gm CMOS technology. It operates with a supply voltage of 1.5V, and the bias current varies from 0.5£gA to 30£gA. Measurement results show that the cutoff frequency can be tuned from 3.12MHz to 8.11MHz when the Capacitance (C) is 5pF.The total harmonic distortion is 0.28%, and the power consumption is 1.09mW.

In this thesis, a brand new first-order low pass square root domain filter (SRD filter) based on operational transconductors amplifiers (OTAs) is presented. The SRD filter consists of a translinear filter and two OTAs. We improve Cruz¡¦s SRD filter [15], reduce the number of transconductors from 3 to 2, and replace Class-AB linear transconductors with OTAs. The circuit has the least number of transistors up to date, therefore, the least power consumption and least chip area. The circuit has been fabricated with 0.35£gm CMOS technology. It operates with a supply voltage 1.5V and the biasing current varies from 0.05uA to 15uA. Measurement results show that the cutoff frequency of the filter can be tuned from 250 Hz to 29 kHz when the external capacitance C is 1nF and the cutoff frequency can be tuned from 1.8 kHz to 237kHz when the external capacitance C is 100pF. The total harmonic distortion is 1.03% and 1.01% when the external capacitance C is 1nF and 100pF and the power consumption is 116£gW.

In this thesis, a first order low pass square root domain filter (SRD filter) based on the novel operational transconductor amplifiers (OTAs) is presented. The SRD filter consists of a translinear filter and two OTAs. Because the conventional OTA has small input voltage swings, which violates the large signal operation of a SRD filter. We propose the novel OTA which is based on the large signal behaviors of MOSFETs, and the OTA also has large signal operation. We improve Cruz¡¦s SRD filter [22], reduce the number of the transconductors from 3 to 2, and replace Class-AB linear transconductors with the proposed OTAs. The MOSFET count of whole circuit can be reduced. Therefore, the OTAs have many advantages: wider input voltage swing, low supply voltage, low power consumption, and small chip area. The circuit has been fabricated with 0.35£gm CMOS technology. It operates with a supply voltage 1.5V and the bias current varies from 0.3£gA to 15£gA. Measurement results show that the cutoff frequency can be tuned from 1.1kHz to 35.2kHz when the external capacitance C is 1nF and the cutoff frequency can be tuned from 8.7kHz to 310.4kHz when the external capacitance C is 100pF. The total harmonic distortions are 0.93% and 0.91% when the external capacitances C are 1nF and 100pF, and the power consumption is 152.29£gW.